The present invention relates to occupant protection and, more particularly, to a system and method for sensing a vehicle rollover condition for helping protect a vehicle occupant.
In order to detect a vehicle rollover condition, a vehicle may be equipped with one or more sensors for detecting the occurrence of vehicle rollover. The sensors typically are connected to a controller that controls actuation of one or more actuatable devices, such as an occupant restraint, to help cushion and/or restrain the occupant during vehicle rollover.
For example, U.S. Pat. No. 5,825,284 discloses a vehicle rollover system having a sensor that provides a signal indicative of lateral acceleration of the vehicle. A processor calculates a roll moment based on the sensor signal, which provides a visual display indicating the likelihood of vehicle rollover. Various devices also have been proposed for detecting an angular orientation of an object. For example, U.S. Pat. No. 5,329,121 to Leviton, U.S. Pat. No. 4,207,463 to Iyeta, U.S. Pat. No. 5,670,780 to Lewis, U.S. Pat. No. 5,103,090 to Weiner et al., and U.S. Pat. No. 4,320,293 to Guretzky each discloses a measuring device that senses angular rotation of a body using optical emitters and detectors.
One aspect of the present invention provides a rollover sensing system that includes a roll rate sensor operative to sense a rate of vehicle rotation about an axis extending through the vehicle and to provide a roll rate signal having an electrical characteristic indicative of the sensed rate of vehicle rotation. A controller is connected to the roll rate sensor and is operative to determine a roll angle of the vehicle based on the roll rate signal. The controller includes a threshold having a value functionally related to roll angle. The controller determines the occurrence of a vehicle rollover condition in response to the sensed roll rate crossing the threshold.
Another aspect of the present invention provides a method for sensing a vehicle rollover condition. The method includes the steps of sensing a roll rate of rotation of the vehicle and determining a roll angle based on the sensed roll rate. A roll rate threshold is provided which has value is functionally related to roll angle. A control signal is provided in response to determining that the sensed roll rate crosses the roll rate threshold.